Abstract:

Zincor uses O2 enrichment (up to 26% O2 in the fluidizing air) to
increase the processing rate of zinc concentrates in the fluidized bed
roasters. The aim of this study is to determine whether O2
enrichment can be reduced by introducing micro-pelletized
concentrate into the feed blend, while maintaining current roaster
feed rates and calcine quality. It was found that, with a load of 20%
micro-pellets introduced into the feed blend, that O2 enrichment
could be reduced by 60%. It was determined that entrained particles
spend on average between 0.46 hour and 2.44 hour in the roaster,
compared to particles remaining between 3.93 hour and 4.00 hour in
the bed overflow. This compares well with a radioactive tracer test
performed by Spira. The required reaction time for micro-pellets was
found to be less than the residence time inside a Zincor roaster. The
result achieved indicated that the average particle residence time
inside the roaster was increased successfully in order to compensate
for the longer reaction time required to roast micro-pellets at lower
levels of O2 in the fluidizing air.